This invention relates to the preparation of a compound, especially an active pharmaceutical compound. Particularly, although not exclusively, the invention relates to the preparation of lactams, for example penicillins and cephalosporins and/or derivatives thereof.
6-Aminopenicillanic acid (6-APA) and 7-aminodesacetoxycephalosporanic acid (7-ADCA) are intermediates used for the manufacture of most semi-synthetic xcex2-lactam antibiotics. The commercially preferred method for the manufacture of 6-APA is by means of biochemical de-acylation of benzyl penicillin, commonly known as Pen-G or equivalent enzymatic deacylation of phenoxymethyl penicillin, commonly known as Pen-V. This is achieved using an enzyme such as penicillin acylase, which has been immobilised on an insoluble matrix such as polystyrene or polyacrylate polymers or co-polymers.
Various processes using this technique are illustrated in the scientific literature. In such processes, penicillin-G is isolated from a fermentation liquor as a solid intermediate using known means and is then dissolved in water in a relatively dilute solution (e.g. 5% w/v). The enzymation reaction (shown in scheme 1 below where R represents a potassium or sodium ion) is carried out at an elevated temperature (e.g. 35-40xc2x0 C.). Phenylacetic acid (PAA) produced is neutralised by the continuous addition of dilute aqueous sodium hydroxide (e.g. 5% w/v) to maintain a pH of around 8.0. The isolation of 6-APA is normally carried out by concentration of the enzymation reaction liquors to, for example, 15% with respect of 6-APA in order to maximise yield, followed by precipitation with a dilute inorganic acid, such as 5% nitric acid or sulphuric acid. The PAA is removed by extraction into an immiscible organic solvent, such as methyl iso-butylketone or butyl acetate. The 6-APA is finally removed by filtration, washed with acetone then dried under vacuum. An acceptable standard conversion yield for the de-acylation process described is 94-96% and is 82-86% for the precipitation and isolation stage. 
The immobilised enzymes used in the above described process may be sensitive to product inhibition. Hence, the reaction is normally carried out on relatively dilute solutions. A drawback of this is that the solubility of 6-APA in water is around 2% which means that a concentration step is necessary in order to minimise product losses in the mother liquors. A costly concentration step is therefore often applied to increase 6-APA content to 12-16%.
PAA constitutes one of the ingredients normally used in the fermentation of penicillin-G. It is therefore, commercially advantageous to recover PAA from the reaction effluent so that it can be recycled. Conventional methods used commercially for the recovery of PAA employ a multistage process involving a combination of two or more of the following techniques: Vacuum distillation, purification (e.g. carbon treatment), extraction into an aqueous phase, chromatography, precipitation, filtration and drying. These techniques are relatively expensive and environmentally problematical.
It is the object of this invention to address the problems described above.
A method of preparing a second compound by catalytic conversion of a first compound, the method comprising contacting said first compound and a catalyst in a solvent mixture comprising water and a first non-aqueous solvent and wherein said catalyst is an enzyme.